When I first started growing roses and met Ralph Moore, one of the things he taught me in that first session was that "the rose is always the best teacher". He went on to explain that roses are impacted by so many variables, that people could be talking about the same rose and have different experiences with the plants. I have found that to be true over the years. Learning from the rose and how it grows in your garden is where we find the best answers.
My thoughts about transplanting your rose are, "Wait until spring". The rose is not going to get larger over winter and is naturally slowing down. When the temps are lower, the photosynthesis process slows down, so the foliage is not creating the nourishment Kyla mentions. This slows down all cellular activity within the plant.
Modern roses store their nutrients in their canes rather than in the root zone during the period we think of as dormancy. In spring as temps begin to warm up, they are genetically programmed to push those nutrients down to the root zone. Why not let the plant do part of the work in helping make the transplanting more successful ?
If you have to cut it back to make the move more manageable, the plant is already setting itself up to produce new growth. Also, you have the opportunity to remove old woody canes at the base of the plant to make room for new growth from the base which will rejuvenate the rose.
The plant may not be as productive in producing blooms in the year of the transplant because it will be busy growing new roots. It will naturally abandon top growth in order to put the most plant energy into growing those roots. With the plant naturally sending both the stored nutrients from the canes and from new growth to the root zone, I think you will have a more successful transplant experience because you are working with the nature of the rose.
I know you have been successful in planting roses late in the season, because roses can be planted when they are dormant. So you have to take your experience with what works in your garden and apply it to the above.
There are a lot of right ways to grow roses.
Smiles,
Lyn
edited to correct typo .. oops !
